TABLE 2.

MICs of meropenem and conjugation efficiency in transformants with plasmids from representative isolates in each group^a

Original species	Group	Original host isolate	MIC (mg/liter)	Avg conjugation efficiency ± SD
E. coli	pKPI-6	E174	4	(8.1 ± 3.8) × 10−2
	IncN	E066	16	(2.2 ± 3.1) × 10−4
	IncN	E033	16	(2.4 ± 1.3) × 10−2
	IncF	E305	<1	(7.5 ± 2.3) × 10−4
K. pneumoniae	pKPI-6	E188	4	(3.7 ± 2.0) × 10−1
	IncN	E187	4	(2.9 ± 1.1) × 10−1
	IncN	E196	16	(4.4 ± 3.5) × 10−1
	Non-IncN KP	E208	4	0
	Non-IncN KP	E328	2	(3.1 ± 2.6) × 10−4

^aGroups correspond to those in Fig. 1. Plasmids from representative isolates in each group were transformed into E. coli TOP10 strain by electroporation. MICs of meropenem for these transformants were measured by the broth microdilution method, in triplicate. The conjugation assay was conducted by mating the transformants as donors and E. coli TUM3456 as a recipient. The conjugation frequency was calculated as the CFU number of transconjugants per number of donors plus transconjugants. Average conjugation efficiencies from triplicate assays are indicated.